In mining, excavation, and other fields, it often is necessary to provide means for breaking and maneuvering, or manipulating, hardened materials, such as rock.
One example of an area in which such need exists is in mining applications in which excavated rock is dumped onto a large screening device known as a grizzly. Grizzlies often are recessed below working level to accommodate sidecar or truck dumping of material thereon. The grizzly may become clogged by dumping oversized rock or boulders thereon, by finer material bridging the openings in the grizzly, and by other types of debris that may have been mixed with the mined materials.
In the past, many mine operators have resorted to manual labor to clear material from the grizzlies. For example, workmen move into the grizzly region with sledgehammers, rope slings, etc. to break up oversized rock and to attempt to remove debris therefrom.
In other operations, permanently installed impact hammers are used to break the oversized rock, such that it may move through the pre-selected sized openings in the grizzly. However, they provide no means for grasping and manipulating stone or debris, other than to attempt to break it by use of the impact hammer.
In light of the number of accidents that have occurred in the use of manual labor to clear grizzlies, and the ineffectiveness of jackhammers alone, it has become important to provide some means for breaking hardened materials, such as rocks, and to manipulate or grasp materials in the region of the impact hammer.